FIG. 1 is a schematic illustrating a conventional structure of an LTE system supporting RN. As shown in FIG. 1, in an access network of an LTE system, wireless resource management entities may include macro base stations (eNB) 101 and relay nodes (RN) 102. The RNs access a core network via another type of macro base stations (DeNB) 103. The eNBs 101 are connected with each other via X2 interfaces. Each of the eNBs 101 are connected with a mobility management entity (MME) and a serving gateway (S-GW) 104 in the core network via S1 interfaces. The RNs 102 access the DeNBs 103 via Un interfaces. DeNBs 103 provide X2 proxy functions between RNs 102 and other eNBs. DeNBs 103 provide S1 proxy functions between RNs 102 and MME/SGWs 104. S1 proxy functions and X2 proxy functions include transmission of UE-dedicated X2 signaling and S1 signaling between RNs 102 and eNBs 101 and between RNs 102 and MMEs 104, and transmission between RNs 102 and SGWs 104.
FIG. 2 is a schematic diagram illustrating a conventional control plane protocol stack of an S1 interface supporting relay. There is an S1 interface between an RN and a DeNB of the RN, and there is an S1 interface between a DeNB and each MME in an MME pool. A DeNB processes and forwards all UE-dedicated S1 signaling between an RN and an MME. The processing of UE-dedicated S1 messages by a DeNB includes modifying S1-application protocol UE identifications (S1-AP UE IDs), transport layer addresses and GPRS tunneling protocol (GTP) tunnel endpoint IDs (TEID) while keeping other parts of the messages unchanged.